Molecular factors of 5-fluorouracil metabolism in colorectal cancer: Analysis of primary tumor and lymph node metastasis

Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) are predictive markers for tumor response to 5-fluorouracil-based therapies. To determine whether gene expression values measured in primary cancer tissue would be useful for prediction of response of lymph node metastases, the expressions of these genes were quantitatively analyzed in 35 pairs of primary colorectal cancer (CRC) and corresponding lymph node metastases using real-time PCR. DPD and TP mRNA levels were significantly lower in the primary colorectal tumor and lymph node metastases compared with the normal adjacent stroma tissue (p<0.01), whereas TS mRNA levels were significantly higher in the primary tumor and lymph node metastases than in the normal adjacent tissue (p<0.001). Median gene expression levels of TP and TS did not differ significantly between primary colorectal tumor and corresponding lymph node metastasis but median DPD gene expression levels in the lymph node metastases were significantly higher compared to matched primary colorectal tumors (p=0.015). There was a significant correlation for DPD, TP and TS gene expression levels between primary colorectal tumor specimens and the matched lymph node metastasis. These results suggest that biopsies of the tumor of origin may be valid for determining predictive markers for chemotherapy response in patients with metastatic CRC.